Dusky dolphin  (Lagenorhynchus obscurus)

Feeding in large schools of 300 – 1000 individuals, these dolphins were thought to be very abundant, but declining numbers in by-catch and during hunting suggest that dusky dolphins are no longer as plentiful as was imagined (1). These extremely numerous aggregations are temporary collections of the more normal 6 – 15 strong pods gathering together for tactical hunting of their anchovy, squid and shrimp prey. The prey are herded together by groups of cooperating dolphins, who leap and slam their bodies on the surface of the water to push the prey closer together as well as to notify other dolphins to join the feeding (4).

Said to be one of the most acrobatic and social of all dolphins, the dusky dolphin is attracted to boats to bow-ride at speeds of up to 20 knots, and will spend afternoons playing, leaping, and mating. They communicate regularly with whistles, squeaks and clicks (2).

Mating occurs in spring, and is somewhat promiscuous within each school, but no pair bonds are formed. Gestation lasts up to 11 months and single calves are born between June and August and measure less than 60 cm (2) (3). Calves are weaned at 18 months (2). Females give birth every two to three years (3).